Wireless battery charger with wireless control system

ABSTRACT

A wireless electrical charging system and a method of operating same wherein operating parameters from a remote portion of the system are wirelessly transmitted to a system controller controlling the output voltage of an alternating power supply. The system controller executes an adaptive model control algorithm that allows the system controller to update the output voltage at a greater rate than the transmission rate of the operating parameters from the remote portion of the system.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application and claimsbenefit under 35 U.S.C. § 120 of U.S. patent application Ser. No.14/700,682, filed Apr. 30, 2015, the entire disclosure of which ishereby incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a wireless battery charger, particularly to awireless battery charger with a control system that transmits batterycharge data wirelessly from the battery to the charger to control thebattery charging process.

BACKGROUND OF THE INVENTION

Wireless electrical power transfer systems, such as those used forwireless charging, are known to incorporate a first coil structure,hereafter referred to as a source coil, that includes a tuned resonantcircuit that is configured to convert alternating electrical energy froman electrical power supply to a magnetic field and to transfer themagnetic energy via the magnetic field to a spaced apart second coilstructure, hereafter referred to as a capture coil. The capture coilalso includes a tuned resonant circuit configured for receiving themagnetic field and converting the magnetic field to electrical energythat is supplied to an electrical load, such as a battery pack or motor.Such a wireless power transfer system may be used for electricallycharging an energy storage device, such as the battery pack of anelectric or hybrid electric vehicle. In such a system, the source coilmay be located on, or embedded into, a surface beneath the vehicle, e.g.the floor of a garage or the surface of a parking lot, and the capturecoil may be disposed on the underside of the vehicle.

The current and voltage of the electrical power supplied by the capturecoil is determined by the voltage of the electrical power supplied bythe power source to the source coil. A control system incorporatingfeedback of the capture coil voltage and current may be used to controlthe voltage of the electrical power supplied by the power supply. Inorder to maintain a wireless connection between the power source and thecapture coil, typically the operation of wireless vehicle chargingsystems has depended primarily on a feedback loop that operates througha wireless communication channel, commonly a wireless channel conformingto Institute of Electrical and Electronics Engineers (IEEE)specification 802.11 (often referred to as “Wi-Fi”). The wirelesscommunication results in a “sampling” effect in the data feedback. Thewireless channel is susceptible to variable delays. The effects of thisdelay (and its destabilizing effect on the control loop) restricts thepossible control bandwidth for the closed-loop control. The controlsystem then does not respond quickly enough to disturbances in thesystem to ensure reliable operation.

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also be inventions.

BRIEF SUMMARY OF THE INVENTION

In accordance with an embodiment of the invention, an electricalcharging system configured to wirelessly charge an energy storage deviceis provided. The electrical charging system includes an electrical powersupply and inverter that is configured to source electrical power havingan alternating output current and an alternating output voltage, anoutput current sensor that is configured to determine an output currentvalue (i_(o)) based on an output current and an output voltage sensorthat is configured to determine an output voltage value (v_(o)) based onthe output voltage. The electrical charging system further includes asource coil in electrical communication with the electrical power supplyand inverter and is configured to generate an alternating magneticfield, a capture coil configured to be magnetically coupled to thesource coil, thereby inducing the capture coil to capture the electricalpower, and a rectifier electrically coupled to the capture coil and theenergy storage device and configured to provide captured electricalpower having a direct voltage and a direct current. The electricalcharging system also includes a battery charging controller configuredto determine a current command value (i_(c)), a direct current sensorconfigured to determine a direct current value (i_(d)) based on thedirect current and a direct voltage sensor configured to determine adirect voltage value (v_(d)) based on the direct voltage, a transmitterconfigured to transmit a sampled current command value (i_(cs)), asampled direct voltage value (v_(ds)), and a sampled direct currentvalue (i_(ds)) at a transmission rate, wherein the sampled currentcommand value (i_(cs)), the sampled direct voltage value (v_(ds)), anddirect current value (i_(ds)) are sampled from the current command value(i_(c)), direct voltage value (v_(d)), and the direct current value(i_(d)) respectively, and a receiver configured to wirelessly receivethe sampled current command value (i_(cs)), the sampled direct voltagevalue (v_(ds)), and the sampled direct current value (i_(ds)) from thetransmitter. The electrical charging system additionally includes asystem controller in electrical communication with the receiver and theelectrical power supply. The system controller is configured todetermine a voltage command value (v_(c)) based on the output currentvalue (i_(o)), the output voltage value (v_(o)), the sampled currentcommand value (i_(cs)), the sampled direct voltage value (v_(ds)), andthe sampled direct current value (i_(ds)). The electrical power supplyis configured to adjust the output voltage value (v_(o)) based on thevoltage command value (v_(c)). A rate at which the voltage command value(v_(c)) is determined by the system controller is greater than thetransmission rate of the transmitter. The system controller determinesthe voltage command value (v_(c)) based on a difference between thesampled current command value (i_(cs)) and a predicted current value(i_(p)) according to the Laplace transform formula:v_(c)=(i_(cs)−i_(p))*(K_(P2)+K_(I2)/S). A value of K_(P2) is aproportional constant and a value of K_(I2) is an integral constant. Thepredicted current value (i_(p)) is determined, via the systemcontroller, according to an adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds). A value of K₀ is determined, via thesystem controller, based on the formulaK₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S). A value of K_(P3) is a proportionalconstant and a value of K_(I3) is an integral constant. K₀ is variablewithin a first predetermined range. A value of K₁ is determined, via thesystem controller, based on the formulaK₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S). A value of K_(P1) is aproportional constant and a value of K_(I1) is an integral constant. K₁is variable within a second predetermined range.

The system controller may fix the value of K₀ at a predetermined initialvalue K_(0init) while changing the value of K₁ from a predeterminedinitial value K_(1init).

The system controller may fix the value of K₁ at an upper limit K_(1max)of the second predetermined range value while changing the value of K₀from the initial value K_(0init).

The system controller may fix the value of K₁ at a lower limit K_(1min)of the second predetermined range value while changing the value of K₀from the initial value K_(0init).

The sampled current command value (i_(cs)), the sampled direct voltagevalue (v_(ds)), and the sampled direct current value (i_(ds)) may betransmitted periodically by the transmitter at the transmission rate.The predicted current value (i_(p)) is determined by the systemcontroller at a rate greater than the transmission rate at which thesampled current command value (i_(cs)) is transmitted periodically bythe transmitter. The voltage command value (v_(c)) is determined by thesystem controller at a rate greater than the transmission rate at whichthe sampled direct voltage value (v_(ds)) is transmitted periodically bythe transmitter.

Transmission of the sampled current command value (i_(cs)), the sampleddirect voltage value (v_(ds)), and the sampled direct current value(i_(ds)) may be time delayed by the transmitter.

In accordance with another embodiment, a method of operating anelectrical charging system configured to wirelessly charge an energystorage device is provided. The electrical charging system has anelectrical power supply and inverter that is configured to provideelectrical power having an alternating output current and an alternatingoutput voltage at a desired frequency. The system includes a source coilin electrical communication with the electrical power supply andconfigured to generate an alternating magnetic field and a capture coilconfigured to be magnetically coupled to the source coil, therebyinducing the capture coil to capture electrical power. This systemfurther includes a rectifier electrically coupled to the capture coiland the battery and configured to provide captured electrical powerhaving a direct voltage and a direct current. This system also has asystem controller that is in electrical communication with theelectrical power supply and is configured to adjust the alternatingoutput voltage. The method includes the steps of providing an outputcurrent sensor configured to determine an output current value (i_(o))based on an output current and providing an output voltage sensorconfigured to determine an output voltage value (v_(o)) based on theoutput voltage, providing a battery charging controller configured todetermine a current command value (i_(c)), providing a direct currentsensor configured to determine a direct current value (i_(d)) based onthe direct current and providing a direct voltage sensor configured todetermine a direct voltage value (v_(d)) based on the direct voltage,sampling the values of the current command value (i_(c)), direct voltagevalue (v_(d)), and the direct current value (i_(d)), providing atransmitter configured to transmit a sampled current command value(i_(cs)), a sampled direct voltage value (v_(ds)), and a sampled directcurrent value (i_(ds)) at a transmission rate and providing a receiverconfigured to wirelessly receive the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) from the transmitter, transmitting thesampled current command value (i_(cs)), the sampled direct voltage value(v_(ds)), and the sampled direct current value (i_(ds)) from thetransmitter to the receiver, determining a voltage command value(v_(c)), via the system controller, based on the output current value(i_(o)), the output voltage value (v_(o)), the sampled current commandvalue (i_(cs)), the sampled direct voltage value (v_(ds)), and thesampled direct current value (i_(ds)), wherein a rate at which thevoltage command value (v_(c)) is determined by the system controller isgreater than the transmission rate of the transmitter, and adjusting theoutput voltage value (v_(o)) of the electrical power supply based on thevoltage command value (v_(c)). The voltage command value (v_(c)) isdetermined, via the system controller, based on a difference between thesampled current command value (i_(cs)) and a predicted current value(i_(p)) according to the Laplace transform formula:v_(c)=(i_(cs)−i_(p))*(K_(P2)+K_(I2)/S). A value of K_(P2) is aproportional constant and a value of K_(I2) is an integral constant. Thepredicted current value (i_(p)) is determined, via the systemcontroller, according to an adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds). A value of K₀ is based on theformula K₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S). A value of K_(P3) is aproportional constant and a value of K_(I3) is an integral constant. K₀is variable within a first predetermined range. A value of K₁ is basedon the formula K₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S). A value of K_(P1)is a proportional constant and a value of K_(I1) is an integralconstant. K₁ is variable within a second predetermined range.

The system controller may fix the value of K₀ at a predetermined initialvalue K_(0init) while changing the value of K₁ from a predeterminedinitial value K_(1init).

The system controller may fix the value of K₁ at an upper limit K_(1max)of the second predetermined range value while changing the value of K₀from the initial value K_(0init).

The system controller may fix the value of K₁ at a lower limit K_(1min)of the second predetermined range value while changing the value of K₀from the initial value K_(0init).

The sampled current command value (i_(cs)), the sampled direct voltagevalue (v_(ds)), and the sampled direct current value (i_(ds)) may betransmitted periodically by the transmitter at the transmission rate.The predicted current value (i_(p)) is determined by the systemcontroller at a rate greater than the transmission rate at which thesampled current command value (i_(cs)) is transmitted periodically bythe transmitter. The voltage command value (v_(c)) is determined by thesystem controller at a rate greater than the transmission rate at whichthe sampled direct voltage value (v_(ds)) is transmitted periodically bythe transmitter.

Transmission of the sampled current command value (i_(cs)), the sampleddirect voltage value (v_(ds)), and the sampled direct current value(i_(ds)) may be time delayed by the transmitter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The present invention will now be described, by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a wireless electrical power transfersystem according to one embodiment;

FIG. 2 is pictorial side view of the wirelesses power transfer system ofFIG. 1 according to one embodiment;

FIG. 3 is graph comparing input power and output power of the wirelessespower transfer system of FIG. 1 using various K₀ values according to oneembodiment; and

FIG. 4 is a flowchart for a method of controlling a wireless electricalpower transfer system according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The wireless electrical power transfer system presented hereinincorporates an adaptive model in the feedback loop to help predict thecurrent that should be supplied by the capture coil to the electricalload and adjust the output voltage of the electrical power supplied bythe electrical power supply accordingly. This allows the controlbandwidth for the closed-loop control to be increased. For example, theoutput voltage for the power supply could be adjusted every 20milliseconds while the capture coil current and voltage data may beupdated every 50 or 100 milliseconds.

FIG. 1 illustrates a non-limiting example of a wireless electrical powertransfer system 10, hereinafter referred to as the system 10. In thisexample, the system 10 serves as an electrical charging systemconfigured to wirelessly charge an energy storage device, such as abattery 12 in an electric or hybrid electric vehicle 14.

The system 10 includes an electrical power supply 16 connected to anelectrical power source 18, in this example a utility main providingelectrical power to the power supply 16 at 240 VAC at 50-60 Hz. Thepower supply 16 supplies a direct current (DC) voltage to an inverter 17that produces an alternating current (AC) voltage within a frequencyrange of 10 kilohertz (kHz) to 450 kHz to provide magnetic couplingbetween a source coil 20 and a capture coil 22. The output voltage(v_(o)) of the power supply 16 can be adjusted based on an input signalfrom an external device, such as a controller. In some applications, thefrequency of the electrical power output from the inverter 17 may alsobe controlled to improve magnetic coupling between the source andcapture coils 20, 22.

The power supply 16 is electrically connected to the power source 18. Asused herein, electrically connected means that the power supply 16 isconnected to the power source 18, e.g. a utility main, by a wireconductor. The alternating electrical power supplied to the source coil20 by the inverter 17 causes the source coil 20 to generate a magneticfield 24. The capture coil 22 is placed within this magnetic field 24and the magnetic field 24 induces an alternating electrical current inthe capture coil 22, thus converting the magnetic energy in the magneticfield 24 to electrical energy. In order to supply the electrical powercaptured by the capture coil 22 to the battery 12, the system 10includes a rectifier 26 and filter 26 to convert the alternating currentfrom the capture coil 22 to a non-time variant current and voltage,hereinafter referred to as a direct current and a direct voltage, thatcan be used to charge the battery 12. As illustrated in FIG. 2, thecapture coil 22 is located on the underside 28 of the vehicle 14 and thesource coil 20 is located on a surface 30, such as a parking lot orgarage floor, under and apart from the vehicle 14.

Returning now to FIG. 1, the system 10 includes a number of voltage andcurrent sensors. One pair of sensors include an output current sensor 32that is configured to determine an output current value (i_(o)) based onthe output current of the power supply 16 and an output voltage sensor34 that is configured to determine an output voltage value (v_(o)) basedon the output voltage of the power supply 16. The output current sensor32 and the output voltage sensor 34 together measure the DC electricalpower supplied to the inverter 17 and that predicts the power thatactually goes to the battery 12. Measuring the “real power” of thealternating voltage output by the inverter 17 AC is very difficultbecause there is both real power and reactive power (energy that iscirculating in the source/capture coil system 20, 22) which would needto be determined. Measuring the DC power supplied to the inverter 17 ismuch easier and more accurate. So the output voltage value (v_(o)) andthe output current value (i_(o)) are DC values and the power supplied tothe inverter 17 is the product of the output voltage value (v_(o)) andthe output current value (i_(o)) (where the output voltage value (v_(o))will remain pretty constant and the output current value (i_(o)) canthen just be an average).

Another pair of sensors include a direct current sensor 36 that isconfigured to determine a direct current value (i_(d)) based on thedirect current that is output by the rectifier 26 and a direct voltagesensor 38 that is configured to determine a direct voltage value (v_(d))based on the direct voltage that is output by the rectifier 26. Thedesign, construction, and implementation of these current and voltagesensors are well known to those skilled in the art.

As shown in FIG. 1, the system 10 also includes a pair of controllers. Abattery charging controller 40 is disposed within the vehicle 14 and iselectrically connected to the battery 12 and monitors the batteryvoltage and determines a current command value (i_(c)) based on thecurrent that needs to be supplied by the rectifier 26 in order toefficiently charge the battery 12. The battery charging controller 40includes a central processing unit (not shown) that may be amicroprocessor, application specific integrated circuit (ASIC), or builtfrom discrete logic and timing circuits (not shown). Softwareinstructions that program the battery charging controller 40 may bestored in a non-volatile (NV) memory device (not shown). The NV memorydevice may be contained within the microprocessor or ASIC or it may be aseparate device. Non-limiting examples of the types of NV memory thatmay be used include electrically erasable programmable read only memory(EEPROM), masked read only memory (ROM), and flash memory. The batterycharging controller 40 also includes a wired transceiver (not shown),such as a controller area network (CAN) transceiver, to allow thebattery charging controller 40 to establish electrical communicationwith other devices within the vehicle 14.

The other controller is a system controller 42 that is in electricalcommunication with the power supply 16 and is configured to determine avoltage command value (v_(c)) based on the output current value (i_(o)),the output voltage value (v_(o)), the current command value (i_(c)), thesampled direct voltage value (v_(ds)), and the sampled direct currentvalue (i_(ds)). The power supply 16 is configured to adjust the outputvoltage value (v_(o)) based on the voltage command value (v_(c)).

The system controller 42 includes a central processing unit (not shown)that may be a microprocessor, application specific integrated circuit(ASIC), or built from discrete logic and timing circuits (not shown).Software instructions that program the system controller 42 to determinethe voltage command value (v_(c)) may be stored in a non-volatile (NV)memory device (not shown). The NV memory device may be contained withinthe microprocessor or ASIC or it may be a separate device. Non-limitingexamples of the types of NV memory that may be used include electricallyerasable programmable read only memory (EEPROM), masked read only memory(ROM), and flash memory. The system controller 42 also includes a wiredtransceiver (not shown), such as a controller area network (CAN)transceiver, to allow the system controller 42 to establish electricalcommunication with the power supply 16 and other devices. The voltagecommand value (v_(c)) may be digitally transmitted from the systemcontroller 42 to the power supply 16. Alternatively, an analog voltagerepresenting the voltage command value (v_(c)) may be generated by thesystem controller 42 and transmitted to the power supply 16.

FIGS. 1 and 2 show that the system 10 further includes a transmitter 44that is disposed within the vehicle 14 and a receiver 46 locatedremotely from the vehicle 14 that is wirelessly connected to thetransmitter 44 The transmitter 44 includes a wired transceiver (notshown), such as a controller area network (CAN) transceiver, to allowthe transmitter 44 to establish electrical communication with thebattery charging controller 40. The transmitter 44 is also in electricalcommunication with the direct current sensor 36 and is configured toreceive the direct current value (i_(d)) from the direct current sensor36. The transmitter 44 is further in electrical communication with thedirect voltage sensor 38 and is configured to receive the direct voltagevalue (v_(d)) from the direct voltage sensor 38. Similarly, the receiver46 contains a wired transceiver (not shown), such as a controller areanetwork (CAN) transceiver, to allow the transmitter 44 to establishelectrical communication with the system controller 42.

The transmitter 44 is configured to periodically transmit the currentcommand value (i_(cs)) from the battery charging controller 40, thedirect voltage value (v_(ds)) from the direct voltage sensor 38, and thedirect current value (i_(ds)) from the direct current sensor 36. As usedherein, “periodically transmitted” may mean either transmitted atregular time intervals or transmitted at irregular time intervals. Theperiodic transmission creates a sampled current command value (i_(cs)),a sampled direct voltage value (v_(ds)), and a sampled direct currentvalue (i_(ds)) that is received by the receiver 46. Each of thesesampled values are then directed from the receiver 46 to the systemcontroller 42 via the transceivers interconnecting them. Thetransmission rate is the number of times that the values (i_(cs),v_(ds), i_(ds)) are sent from the transmitter 44 to the receiver 46 pera time unit, e.g. 10/sec in the case where the values are sent every 100milliseconds. This may be an averaged rate when the values aretransmitted at irregular time intervals.

The voltage command value (v_(c)) is adjusted to control the directcurrent value (i_(d)) of the current supplied to the battery 12. Thestate of charge of the battery 12 is a prime determinant of the directvoltage value (v_(d)). Increasing the output voltage value (v_(o)) ofthe power supplied to the inverter 17 causes more current to flow intothe battery 12. Therefore the system 10 is basically controlling thevoltage command value (v_(c)) in order to regulate the direct currentvalue (i_(d)). Without subscribing to any particular theory ofoperation, this works because the source/capture coil system 20, 22 hasa fairly high impedance. Therefore, the output impedance to the battery12 is not really low as is typical in a power supply. There is a lot ofvoltage “droop” as more current (i_(d)) is drawn from therectifier/filter 26 by the battery 14.

According to a particular embodiment, the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) are sent from the transmitter 44 to thereceiver 46 at a periodic rate, e.g. 100 milliseconds. The systemcontroller 42 calculates the voltage command value (v_(c)) based on thefollowing formula: v_(c)=i_(e)*(K_(P2)+K_(I2)/S) written as a Laplacetransform where the value of the current error (i_(e)) is a differencebetween the sampled current command value (i_(cs)) and a predictedcurrent value (i_(p)). Calculation of the voltage command value (v_(c))may be implemented by use of a proportional-integral (PI) controller.The value of i_(e) is scaled by a proportional scaling factor K_(P2) andadded to the integral of i_(e) scaled by an integral scaling factorK_(I2) to determine the voltage command value. In this particularembodiment, the system controller 42 periodically calculates the voltagecommand value, e.g. 50/sec or every 20 milliseconds, and sends a commandcontaining the voltage command value to the power supply 16 to adjustthe output voltage value (v_(o)). The values for K_(P2) and K_(I2) maybe based on the response time of the power supply 16 and the efficiencyof the power transfer between the source coil 20 and the capture coil 22and may be determined experimentally. In this particular embodiment, thevalue of K_(P2) is zero.

The predicted current value (i_(p)) is also calculated by the systemcontroller 42 and is based on the following adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds), where v_(o) is the output voltagevalue of the power supply 16 determined by the output voltage sensor 34,i_(o) is the output current value of the power supply 16 determined bythe output current sensor 32, and v_(ds) is the sampled direct voltagevalue (v_(ds)) sent to the receiver 46 by the transmitter 44. The valueof K₀ is a variable offset value that is the primary adaptationcorrection term at low power operation. The value of K₀ is based on theformula K₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S) written as a Laplacetransform, wherein a value of K_(P3) is a proportional constant and avalue of K_(I3) is an integral constant. The value of K₀ is limited to afirst predetermined range. K₁ that is the primary adaptation correctionterm at high power operation. K₁ calculated by the system controller 42based on the formula: K₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S) written as aLaplace transform, where the difference between i_(ds), the sampleddirect current value sent to the receiver 46 by the transmitter 44 andthe previously calculated value of the predicted current value (i_(p-1))is scaled by a proportional scaling factor K_(P1) and is added to thisdifference between i_(ds) and i_(p-1) scaled by an integral scalingfactor K_(I1). The value of K₁ is limited to a second predeterminedrange, e.g. 0.8 to 0.95. Calculation of the values of K₀ and K₁ may beimplemented by use of a proportional-integral (PI) controller. In thisexemplary embodiment, the system controller 42 calculates the predictedcurrent value and the scaling factors K₀ and K₁ 10 times/sec or every100 milliseconds.

A non-limiting example of a running sequence for the system controller42 of the system 10 is as follows:

-   -   Set the system controller 42 to calculate the voltage command        value (v_(c)) and the scaling factors K₀ and K₁ in a hold mode        and initialize K₀ and K₁ to initial values K_(0init) and        K_(1init).    -   Initialize the voltage command value (v_(c)) to adjust the        output voltage value (v_(o)) to a low start-up value.    -   Ramp up the voltage command value (v_(c)) to cause the predicted        current value (i_(p)) to equal the current command value (i_(c))        via overriding the integrator when calculating the voltage        command value (v_(c)). This may be accomplished by overriding        the current command value (i_(c)).    -   Enable the system controller 42 to calculate the voltage command        value (v_(c)), thus establishing an adaptive voltage controller        48, i.e. not reliant on values transmitted from the remote        battery charging controller 40, or direct current sensor 36 and        direct voltage sensor 38.    -   Enable the system controller 42 to calculate the value of K₀ and        K₁, thus establishing an adaptive voltage controller 50.    -   In a first or “normal” control mode, the value of K₀ is        maintained at the initial value K_(0init) while changing K₁ from        the initial value K_(1init) based on the formula        K₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S) to “fine tune” i_(p) to        match i_(ds). This normal mode of operation is maintained only        unless K₁ reaches a predetermined maximum value K_(1max) or a        predetermined minimum value K_(1min). If either limit for K₁ is        reached, the value of K₁ is “held” at the limit value and        control transfers to a second control mode in which the value of        K₀ is adjusted.    -   In this second control mode, the value of K₀ is changed bases on        the formula K₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S) while the limit        value K_(1max) or K_(1min).is maintained.    -   If the value of K₁ is held at K_(1max), the value of K₀ should        decrease from K_(0init). As long as the value of K₀ is less than        K_(0init), the value of K₁ will be held at K_(1max) and the        value of K₀ will continue to be adjusted. If the value of K₀        increases to be equal to or greater than K_(0init), the value of        K₀ will again be held equal to K_(0init) and the control mode        will transfer back to adjusting K₁, i.e. the normal control mode        described above. The value of K₀ will not be allowed be less        than a predetermined minimum value K_(0min), but no other        changes in the control mode occur when K₀ reaches that limit.    -   If the value of K₁ is held at K_(1min), the value of K₀ should        increase from K_(0init). As long as the value of K₀ is greater        than K_(0init), the value of K₁ will be held at K_(1min) and the        value of K₀ will continue to be adjusted. If the value of K₀        decreases to be equal to or less than K_(0init), the value of K₀        will again be held equal to K_(0init) and the control mode will        transfer back to adjusting K₁, i.e. the normal control mode        described above. The value of K₀ will not be allowed to be        greater than a predetermined maximum value K_(0max), but no        other changes in the control mode occur when K₀ reaches that        limit.

Accordingly, the system 10 provides a “high bandwidth” voltagecontroller 48 on the source coil 20 side of the system 10, so calledbecause the voltage command value (v_(c)) is calculated once every 20milliseconds. The power output of the power supply 16 is used as theprimary predictor of the capture coil 22 output power and is regulatedon the source coil 20 side of the system 10. The system 10 furtherprovides a “low bandwidth” voltage controller 50 that operates acrossthe wireless link, so called because the predicted current value (i_(p))and the value of scaling factors K₀ and K₁ are periodically calculated,e.g. once every 20 milliseconds, and is limited by the transmission rateof the wireless link. The slower predictive changes to the value ofscaling factors K₀ and K₁ reduce long term error in the predictedcurrent value (i_(p)). Without subscribing to any particular theory ofoperation, the system 10 is tolerant of the sampled current commandvalue (i_(cs)), the sampled direct voltage value (v_(ds)), and thesampled direct current value (i_(ds)) and transmission delays across thewireless link due to the lower bandwidth of the voltage controller 50.

All critical information for controlling the system 10 is available onthe receiver side of the wireless link. Proper control of the system 10requires information from both sides of the wireless link, e.g. outputcurrent value (i_(o)), output voltage value (v_(o)) and current commandvalue (i_(c)), direct voltage value (v_(d)), the direct current value(i_(d)). The system 10 ensures a consistent set of control parameters,e.g. the capture coil side is mostly input/output values.

FIG. 3 illustrates example comparisons of input power from the powersupply to output power from the rectifier/filter to the battery usingdifferent values for K₀.

FIG. 4 illustrates a non-limiting example of a method 100 of operatingan electrical charging system 10 configured to wirelessly charge anenergy storage device having a power supply 16 and inverter 17configured to source electrical power having an alternating outputcurrent and an alternating output voltage at a desired frequency, asource coil 20 in electrical communication with the inverter 17 andconfigured to generate an alternating magnetic field 24, a capture coil22 configured to be magnetically coupled to the source coil 20, therebyinducing the capture coil 22 to capture electrical power, a rectifier 26electrically coupled to the capture coil 22 and the battery 12 andconfigured to provide captured electrical power having a direct voltageand a direct current, and a system controller 42 in electricalcommunication with the power supply 16 and configured to adjust thealternating output voltage. The method 100 include the following steps.

STEP 110, PROVIDE AN OUTPUT CURRENT SENSOR OUTPUTTING AN OUTPUT CURRENTVALUE, AN OUTPUT VOLTAGE SENSOR OUTPUTTING A OUTPUT VOLTAGE VALUE, ADIRECT CURRENT SENSOR OUTPUTTING A DIRECT CURRENT VALUE, AND A DIRECTVOLTAGE SENSOR OUTPUTTING A DIRECT VOLTAGE VALUE, includes providing anoutput current sensor 32 configured to determine an output current value(i_(o)) based on the output current, providing an output voltage sensor34 configured to determine an output voltage value (v_(o)) based on theoutput voltage, providing a direct current sensor 36 configured todetermine a direct current value (i_(d)) based on the direct current,and providing a direct voltage sensor 38 configured to determine adirect voltage value (v_(d)) based on the direct voltage.

STEP 112, PROVIDE A BATTERY CHARGING CONTROLLER OUTPUTTING A CURRENTCOMMAND VALUE, includes providing a battery charging controller 40configured to determine a current command value (i_(c)).

STEP 114, SAMPLE THE CURRENT COMMAND VALUE, DIRECT VOLTAGE VALUE, ANDTHE DIRECT CURRENT VALUE, includes sampling the values of the currentcommand value (i_(c)), direct voltage value (v_(d)), and the directcurrent value (i_(d)).

STEP 116, PROVIDE A TRANSMITTER AND RECEIVER CONFIGURED TO SEND ANDRECEIVE THE SAMPLED VALUES, includes providing a transmitter 44configured to transmit a sampled current command value (i_(cs)), asampled direct voltage value (v_(ds)), and a sampled direct currentvalue (i_(ds)) at a transmission rate and providing a receiver 46configured to wirelessly receive the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) from the transmitter 44.

STEP 118, TRANSMIT THE SAMPLED VALUES FROM THE TRANSMITTER TO THERECEIVER, includes transmitting the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) from the transmitter 44 to the receiver46. The transmission rate is periodic, e,g. about once every 100milliseconds. The sampled current command value (i_(cs)), the sampleddirect voltage value (v_(ds)), and the sampled direct current value(i_(ds)) are transmitted periodically by the transmitter 44 at thetransmission rate. The transmission of the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) are time delayed by the transmitter 44.

STEP 120, DETERMINE A VOLTAGE COMMAND VALUE BASED ON THE OUTPUT CURRENTVALUE, THE OUTPUT VOLTAGE VALUE, THE SAMPLED CURRENT COMMAND VALUE, THESAMPLED DIRECT VOLTAGE VALUE, AND THE SAMPLED DIRECT CURRENT VALUE,includes determining a voltage command value (v_(c)), via the systemcontroller 42, based on the output current value (i_(o)), the outputvoltage value (v_(o)), the sampled current command value (i_(cs)), thesampled direct voltage value (v_(ds)), and the sampled direct currentvalue (i_(ds)). A rate at which the voltage command value (v_(c)) isdetermined by the system controller 42 is greater than the transmissionrate of the transmitter 44. The voltage command value (v_(c)) isdetermined, via the system controller 42, based on a difference betweenthe sampled current command value (i_(cs)) and a predicted current value(i_(p)) according to the Laplace transform formula:v_(c)=(i_(cs)−i_(p))*(K_(P2)+K_(I2)/S). A value of K_(P2) is aproportional constant and a value of K_(I2) is an integral constant. Thepredicted current value (i_(p)) is determined, via the systemcontroller, according to an adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds). A value of K₀ is determined by thesystem controller 42 based on the formulaK₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S). A value of K_(P3) is a proportionalconstant and a value of K_(I3) is an integral constant. K₀ is variablewithin a first predetermined range. A value of K₁ is determined by thesystem controller 42 based on the formulaK₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S). A value of K_(P1) is aproportional constant and a value of K_(I1) is an integral constant. K₁is variable within a second predetermined range.

The value of K₀ is normally maintained at the initial value K_(0init)while changing K₁ from the initial value K_(1init) based on the formulaK₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S) to “fine tune” i_(p) to matchi_(ds). This normal mode of operation is maintained only unless K₁reaches a predetermined maximum value K_(1max) or a predeterminedminimum value K_(1min). If either limit for K₁ is reached, the value ofK₁ is “held” at the limit value and control transfers to a secondcontrol mode in which the value of K₀ is adjusted.

In this second control mode, the value of K₀ is changed bases on theformula K₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S) while the limit valueK_(1max) or K_(1min).is maintained.

If the value of K₁ is held at K_(1max), the value of K₀ should decreasefrom K_(0init). As long as the value of K₀ is less than K_(0init), thevalue of K₁ will be held at K_(1max) and the value of K₀ will continueto be adjusted. If the value of K₀ increases to be equal to or greaterthan K_(0init), the value of K₀ will again be held equal to K_(0init)and the control mode will transfer back to adjusting K₁, i.e. the normalcontrol mode described above. The value of K₀ will not be allowed beless than a predetermined minimum value K_(0min), but no other changesin the control mode occur when K₀ reaches that limit.

If the value of K₁ is held at K_(1min), the value of K₀ should increasefrom K_(0init). As long as the value of K₀ is greater than K_(0init),the value of K₁ will be held at K_(1min) and the value of K₀ willcontinue to be adjusted. If the value of K₀ decreases to be equal to orless than K_(0init), the value of K₀ will again be held equal toK_(0init) and the control mode will transfer back to adjusting K₁, i.e.the normal control mode described above. The value of K₀ will not beallowed to be greater than a predetermined maximum value K_(0max), butno other changes in the control mode occur when K₀ reaches that limit.

STEP 122, ADJUSTING THE OUTPUT VOLTAGE VALUE OF AN ELECTRICAL POWERSUPPLY BASED ON THE VOLTAGE COMMAND VALUE, includes adjusting the outputvoltage value (v_(o)) of the power supply 16 based on the voltagecommand value (v_(c)).

Accordingly, wireless electrical charging system 10 and a method 100 ofcontrolling such a system 10 is provided. The system 10 and method 100provide the advantages of providing a system controller 42 wirelesslyreceiving control parameters, e.g. current command, direct voltage anddirect current values from a remote portion of the system 10, whileadjusting the output voltage of the power supply 16 at a higher ratethan the rate at which the control parameters are received wirelessly.This is accomplished by the use an adaptive control model executed bythe system controller 42 that predicts the value current command signal.This system 10 and method 100 can compensate for the sampling and delayof the control parameters from the remote portion of the system 10.

While the examples contained herein calculate the predicted outputcurrent (i_(p)), other embodiments may calculate a predicted outputpower (p_(outp)) based on the short term stability (i.e. slow rate ofchange) of the direct voltage value (v_(d)) due to the influence of thebattery and the known linear relationship between power and current at aconstant voltage.

While the examples contained herein calculate the predicted outputcurrent (i_(p)), other embodiments may calculate a predicted outputpower (p_(outp)) based on the short term stability (i.e. slow rate ofchange) of the direct voltage value (v_(d)) due to the influence of thebattery and the known linear relationship between power and current at aconstant voltage.

While the examples contained herein have referred to the use of awireless electrical charging system 10 to charge a battery 12 in anelectric vehicle 14 the system 10 and method 100 described herein may beapplied to any other wireless power transfer for charging a battery orother energy storage devices, such as wirelessly charging a battery in aportable electronic device, e.g. cellular telephone or tablet computer.In addition, the system 10 is not limited to the calculation rates,transmission rates, and/or particular control formulae listed herein.

While this invention has been described in terms of the preferredembodiments thereof, it is not intended to be so limited, but ratheronly to the extent set forth in the claims that follow. Moreover, theuse of the terms first, second, etc. does not denote any order ofimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced items.

We claim:
 1. An electrical charging system configured to wirelesslycharge an energy storage device, comprising: an electrical power supplyconfigured to source electrical power having an alternating outputcurrent and an alternating output voltage; an output current sensorconfigured to determine an output current value (i_(o)) based on anoutput current and an output voltage sensor configured to determine anoutput voltage value (v_(o)) based on the output voltage; a source coilin electrical communication with the electrical power supply andconfigured to generate an alternating magnetic field; a capture coilconfigured to be magnetically coupled to said source coil, therebyinducing the capture coil to capture the electrical power; a rectifierelectrically coupled to the capture coil and the energy storage deviceand configured to provide captured electrical power having a directvoltage and a direct current; a battery charging controller configuredto determine a current command value (i_(c)); a direct current sensorconfigured to determine a direct current value (i_(d)) based on thedirect current and a direct voltage sensor configured to determine adirect voltage value (v_(d)) based on the direct voltage; a transmitterconfigured to transmit a sampled current command value (i_(cs)), asampled direct voltage value (v_(ds)), and a sampled direct currentvalue (i_(ds)) at a transmission rate, wherein the sampled currentcommand value (i_(cs)), the sampled direct voltage value (v_(ds)), anddirect current value (i_(ds)) are sampled from the current command value(i_(c)), direct voltage value (v_(d)), and the direct current value(i_(d)) respectively; a receiver configured to wirelessly receive thesampled current command value (i_(cs)), the sampled direct voltage value(v_(ds)), and the sampled direct current value (i_(ds)) from thetransmitter; and a system controller in electrical communication withthe receiver and the electrical power supply and configured to determinea voltage command value (v_(c)) based on the output current value(i_(o)), the output voltage value (v_(o)), the sampled current commandvalue (i_(cs)), the sampled direct voltage value (v_(ds)), and thesampled direct current value (i_(ds)), wherein the electrical powersupply is configured to adjust the output voltage value (v_(o)) based onthe voltage command value (v_(c)), wherein a rate at which the voltagecommand value (v_(c)) is determined by the system controller is greaterthan the transmission rate of the transmitter, wherein the systemcontroller determines the voltage command value (v_(c)) based on adifference between the sampled current command value (i_(cs)) and apredicted current value (i_(p)) according to the Laplace transformformula: v_(c)=(i_(cs)−i_(p))*(K_(P2)+K_(I2)/S), wherein a value ofK_(P2) is a proportional constant and a value of K_(I2) is an integralconstant, wherein the predicted current value (i_(p)) is determined, viathe system controller, according to an adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds), wherein a value of K₀ is determined,via the system controller, based on the formulaK₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S), wherein a value of K_(P3) is aproportional constant and a value of K_(I3) is an integral constant,wherein K₀ is variable within a first predetermined range, wherein avalue of K₁ is determined, via the system controller, based on theformula K₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S), wherein a value of K_(P1)is a proportional constant and a value of K_(I1) is an integralconstant, and wherein K₁ is variable within a second predeterminedrange.
 2. The electrical charging system according to claim 1, whereinthe system controller fixes the value of K₀ at a predetermined initialvalue K_(0init) while changing the value of K₁ from a predeterminedinitial value K_(1init).
 3. The electrical charging system according toclaim 1, wherein the system controller fixes the value of K₁ at an upperlimit K_(1max) of the second predetermined range value while changingthe value of K₀ from the initial value K_(0init).
 4. The electricalcharging system according to claim 1, wherein the system controllerfixes the value of K₁ at a lower limit K_(1min) of the secondpredetermined range value while changing the value of K₀ from theinitial value K_(0init).
 5. The electrical charging system according toclaim 1, wherein the sampled current command value (i_(cs)), the sampleddirect voltage value (v_(ds)), and the sampled direct current value(i_(ds)) are transmitted periodically by the transmitter at thetransmission rate.
 6. The electrical charging system according to claim5, wherein the predicted current value (i_(p)) is determined by thesystem controller at a rate greater than the transmission rate at whichthe sampled current command value (i_(cs)) is transmitted periodicallyby the transmitter.
 7. The electrical charging system according to claim5, wherein the voltage command value (v_(c)) is determined by the systemcontroller at a rate greater than the transmission rate at which thesampled direct voltage value (v_(ds)) is transmitted periodically by thetransmitter.
 8. The electrical charging system according to claim 1,wherein transmission of the sampled current command value (i_(cs)), thesampled direct voltage value (v_(ds)), and the sampled direct currentvalue (i_(ds)) are time delayed by the transmitter.
 9. A method ofoperating an electrical charging system configured to wirelessly chargean energy storage device having an electrical power supply configured tosource electrical power having an alternating output current and analternating output voltage at a desired frequency, a source coil inelectrical communication with the electrical power supply and configuredto generate an alternating magnetic field, a capture coil configured tobe magnetically coupled to said source coil, thereby inducing thecapture coil to capture the electrical power, a rectifier electricallycoupled to the capture coil and the energy storage device and configuredto provide captured electrical power having a direct voltage and adirect current, and a system controller in electrical communication withthe electrical power supply and configured to adjust the alternatingoutput voltage, said method comprising the steps of: providing an outputcurrent sensor configured to determine an output current value (i_(o))based on an output current and providing an output voltage sensorconfigured to determine an output voltage value (v_(o)) based on theoutput voltage; providing a battery charging controller configured todetermine a current command value (i_(c)); providing a direct currentsensor configured to determine a direct current value (i_(d)) based onthe direct current and providing a direct voltage sensor configured todetermine a direct voltage value (v_(d)) based on the direct voltage;sampling the values of the current command value (i_(c)), direct voltagevalue (v_(d)), and the direct current value (i_(d)); providing atransmitter configured to transmit a sampled current command value(i_(cs)), a sampled direct voltage value (v_(ds)), and a sampled directcurrent value (i_(ds)) at a transmission rate and providing a receiverconfigured to wirelessly receive the sampled current command value(i_(cs)), the sampled direct voltage value (v_(ds)), and the sampleddirect current value (i_(ds)) from the transmitter; transmitting thesampled current command value (i_(cs)), the sampled direct voltage value(v_(ds)), and the sampled direct current value (i_(ds)) from thetransmitter to the receiver; determining a voltage command value(v_(c)), via the system controller, based on the output current value(i_(o)), the output voltage value (v_(o)), the sampled current commandvalue (i_(cs)), the sampled direct voltage value (v_(ds)), and thesampled direct current value (i_(ds)), wherein a rate at which thevoltage command value (v_(c)) is determined by the system controller isgreater than the transmission rate of the transmitter; and adjusting theoutput voltage value (v_(o)) of the electrical power supply based on thevoltage command value (v_(c)), wherein the voltage command value (v_(c))is determined, via the system controller, based on a difference betweenthe sampled current command value (i_(cs)) and a predicted current value(i_(p)) according to the Laplace transform formula:v_(c)=(i_(cs)−i_(p))*(K_(P2)+K_(I2)/S), wherein a value of K_(P2) is aproportional constant and a value of K_(I2) is an integral constant,wherein the predicted current value (i_(p)) is determined, via thesystem controller, according to an adaptive model formula:i_(p)=((K₁*v_(o)*i_(o))−K₀)/v_(ds), wherein a value of K₀ is determinedby the system controller based on the formulaK₀=(i_(ds)−i_(p))*(K_(P3)+K_(I3)/S), wherein a value of K_(P3) is aproportional constant and a value of K_(I3) is an integral constant,wherein K₀ is variable within a first predetermined range, wherein avalue of K₁ is determined by the system controller based on the formulaK₁=(i_(ds)−i_(p-1))*(K_(P1)+K_(I1)/S), wherein a value of K_(P1) is aproportional constant and a value of K_(I1) is an integral constant, andwherein K₁ is variable within a second predetermined range.
 10. Themethod according to claim 9, wherein the system controller fixes thevalue of K₀ at a predetermined initial value K_(0init) while changingthe value of K₁ from a predetermined initial value K_(1init).
 11. Themethod according to claim 9, wherein the system controller fixes thevalue of K₁ at an upper limit K_(1max) of the second predetermined rangevalue while changing the value of K₀ from the initial value K_(0init).12. The method according to claim 9, wherein the system controller fixesthe value of K₁ at a lower limit K_(1min) of the second predeterminedrange value while changing the value of K₀ from the initial valueK_(0init).
 13. The method according to claim 9, wherein the sampledcurrent command value (i_(cs)), the sampled direct voltage value(v_(ds)), and the sampled direct current value (i_(ds)) are transmittedperiodically by the transmitter at the transmission rate.
 14. The methodaccording to claim 13, wherein the predicted current value (i_(p)) isdetermined by the system controller at a rate greater than thetransmission rate at which the sampled current command value (i_(cs)) istransmitted periodically by the transmitter.
 15. The method according toclaim 13, wherein the voltage command value (v_(c)) is determined by thesystem controller at a rate greater than the transmission rate at whichthe sampled direct voltage value (v_(ds)) is transmitted periodically bythe transmitter.
 16. The method according to claim 9, whereintransmission of the sampled current command value (i_(cs)), the sampleddirect voltage value (v_(ds)), and the sampled direct current value(i_(ds)) are time delayed by the transmitter.